Method and apparatus for channel estimation in wireless communication system

ABSTRACT

The present disclosure relates to a pre-5 th -Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4 th -Generation (4G) communication system such as Long Term Evolution (LTE). The present invention relates to a method and apparatus for channel estimation in a wireless communication system. A method for operating a transmitter comprises the operations of: transmitting a first reference signal through a first antenna; and transmitting a second reference signal through a second antenna, wherein the first reference signal includes a first Golay sequence, and the second reference signal includes a second Golay sequence.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

This application is a continuation of application Ser. No. 15/770,143,which is the National Stage of International Application No.PCT/KR2016/011861, filed Oct. 21, 2016, which claims priority to KoreanPatent Application No. 10-2015-0146893, filed Oct. 21, 2015, thedisclosures of which are herein incorporated by reference in theirentireties.

BACKGROUND 1. Field

The present disclosure relates to an electronic device a method and anapparatus for transmitting and receiving a signal for channel estimationin a wireless communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4^(th) generation (4G) communication systems, efforts havebeen made to develop an improved 5^(th) generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the IEEE 802.11ad system, which is a conventional communicationsystem employing an extremely-high-frequency band, a transmissionapparatus transmits a Channel Estimation Field (CEF) formed of a Golaysequence for channel estimation. Also, a reception apparatus mayestimate a channel based on the CEF received from the transmissionapparatus. However, since this channel estimation method is for aSingle-Input and Single-Output (SISO) system, using this method in anMIMO system cannot achieve accurate channel estimation.

SUMMARY

Therefore, an exemplary embodiment of the present disclosure is toprovide a method and an apparatus for estimating a channel in a wirelesscommunication system supporting Multiple-Input and Multiple-Output(MIMO) (hereinafter, referred to as an “MIMO system”).

An exemplary embodiment of the present disclosure is to provide a methodand an apparatus in which a transmitter of an MIMO system transmits asignal to minimize a channel estimation error and a receiver receivesthe signal.

An exemplary embodiment of the present disclosure is to provide a methodand an apparatus for generating different reference signals based onGolay sequences generated using different seeds and for transmitting thedifferent reference signals via separate antennas in an MIMO system.

An exemplary embodiment of the present disclosure is to provide a methodand an apparatus for transmitting signals including the same Golaysequence via two or more antennas at different times based on thecorrelation of a Golay sequence in an MIMO system.

According to an exemplary embodiment of the present disclosure, anoperation method of a transmission apparatus in a wireless communicationsystem may include: transmitting a first reference signal through afirst antenna; and transmitting a second reference signal through asecond antenna, wherein the first reference signal may include a firstGolay sequence generated based on a first seed, and the second referencesignal may include a second Golay sequence generated based on a secondseed.

According to an exemplary embodiment of the present disclosure, anoperation method of a transmission apparatus in a wireless communicationsystem may include: transmitting a first reference signal through afirst antenna; and transmitting a second reference signal through asecond antenna, wherein the first reference signal and the secondreference signal may include the same Golay sequence, and a transmissionstart time for the second reference signal may be delayed by a thresholdtime from a transmission start time for the first reference signal.

According to an exemplary embodiment of the present disclosure, anoperation method of a reception apparatus in a wireless communicationsystem may include: receiving a signal through a first antenna and asecond antenna; performing first correlation of the received signal ofthe first antenna using a first correlator; performing secondcorrelation of the received signal of the second antenna using a secondcorrelator; and estimating a channel based on a result of the firstcorrelation and a result of the second correlation, wherein the firstcorrelator is configured based on a first Golay sequence generated basedon a first seed, and the second correlator is configured based on asecond Golay sequence generated based on a second seed.

According to an exemplary embodiment of the present disclosure, atransmission apparatus in a wireless communication system may include: afirst antenna configured to transmit a first reference signal; a secondantenna configured to transmit a second reference signal; and aprocessor configured to generate the first reference signal and thesecond reference signal, wherein the first reference signal may includea first Golay sequence generated based on a first seed, and the secondreference signal may include a second Golay sequence generated based ona second seed.

According to an exemplary embodiment of the present disclosure, atransmission apparatus in a wireless communication system may include: afirst antenna configured to transmit a first reference signal; a secondantenna configured to transmit a second reference signal; and aprocessor configured to configure the first reference signal and thesecond reference signal using the same Golay sequence and to delay atransmission start time for the second reference signal by a thresholdtime from a transmission start time for the first reference signal.

According to an exemplary embodiment of the present disclosure, areception apparatus in a wireless communication system may include: afirst antenna and a second antenna configured to receive a referencesignal transmitted from a transmission apparatus; a first correlatorconfigured to perform first correlation of the received signal of thefirst antenna; a second correlator configured to perform secondcorrelation of the received signal of the second antenna; and a channelestimator configured to estimate a channel based on a result of thefirst correlation and a result of the second correlation, wherein thefirst correlator is configured based on a first Golay sequence generatedbased on a first seed, and the second correlator is configured based ona second Golay sequence generated based on a second seed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 illustrates the configuration of a wireless communication systemaccording to an exemplary embodiment of the present disclosure;

FIG. 2 illustrates the configuration of Golay sequences Ga128(k) andGb128(k);

FIGS. 3A and 3B illustrate a Channel Estimation Field (CEF) including aGolay sequence;

FIG. 4 illustrates an example of transmitting and receiving the CEF ofFIG. 3A in a wireless communication system;

FIG. 5 illustrates an example of transmitting the CEFs illustrated inFIGS. 3A and 3B in a 2×2 MIMO system according to an exemplaryembodiment of the present disclosure;

FIG. 6 illustrates the correlation between R_(vu) and R_(uv) accordingto an exemplary embodiment of the present disclosure;

FIG. 7 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 5;

FIGS. 8A and 8B illustrate the configuration of a transmission signalfor channel estimation according to an exemplary embodiment of thepresent disclosure;

FIG. 9 illustrates an example of transmitting the CEFs of FIG. 8Aaccording to an exemplary embodiment of the present disclosure;

FIG. 10 illustrates the correlation between R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾,R_(v) ⁽¹⁾ _(v), and R_(u) ⁽¹⁾ _(u) according to an exemplary embodimentof the present disclosure;

FIG. 11 shows a graph illustrating channel estimation errors by seed forgenerating a Golay sequence;

FIG. 12 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 9;

FIG. 13 illustrates a structure in which a reception apparatus estimatesa channel using a single correlator for each antenna according to anexemplary embodiment of the present disclosure;

FIG. 14 illustrates the configuration of a transmission signal forchannel estimation according to another exemplary embodiment of thepresent disclosure;

FIG. 15 illustrates an example of transmitting the CEFs of FIG. 14according to an exemplary embodiment of the present disclosure;

FIG. 16 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 15;

FIGS. 17A and 17B illustrate the configuration of a transmission signalfor channel estimation according to various exemplary embodiments of thepresent disclosure;

FIG. 18 illustrates the structure of a reception apparatus that receivesthe CEF signal of FIG. 17A and estimates a channel;

FIG. 19 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 18;

FIGS. 20A and 20B illustrate the configuration of a transmission signalfor channel estimation according to various exemplary embodiments of thepresent disclosure;

FIG. 21 illustrates an example of transmitting the CEFs of FIG. 20Baccording to various exemplary embodiments of the present disclosure;

FIG. 22 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 21;

FIG. 23 illustrates the structure of a reception apparatus that receivesthe CEFs in FIG. 20A or FIG. 20B and estimates a channel;

FIG. 24 illustrates the operation procedure of a transmission apparatusaccording to an exemplary embodiment of the present disclosure;

FIG. 25 illustrates the operation procedure of a transmission apparatusaccording to another exemplary embodiment of the present disclosure;

FIG. 26 illustrates the operation procedure of a reception apparatusaccording to an exemplary embodiment of the present disclosure;

FIG. 27 illustrates the operation procedure of a reception apparatusaccording to another exemplary embodiment of the present disclosure;

FIG. 28 is a block diagram illustrating the configuration of atransmission apparatus according to an exemplary embodiment of thepresent disclosure; and

FIG. 29 is a block diagram illustrating the configuration of a receptionapparatus according to an exemplary embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will bedescribed with reference to the accompanying drawings. Further, in thefollowing description of the present disclosure, a detailed descriptionof known functions or configurations incorporated herein will be omittedwhen it may make the subject matter of the present disclosure ratherunclear. Further, terms described later are defined in consideration offunctions of the present disclosure, but may vary according to theintention or convention of a user or operator. Therefore, thedefinitions of the terms should be made based on the contents throughoutthe specification.

The present disclosure relates to an electronic device a method and anapparatus for transmitting and receiving a signal for channel estimationin a wireless communication system.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to limit various embodiments. Forexample, terms to indicate a signal type, terms to indicate a layer towhich a message is transmitted, terms to indicate an antenna structureand antenna components, terms to denote items included in feedbackinformation, and the like, which are used herein, are provided for theconvenience of description. Therefore, the present disclosure is notlimited by the following terms, and other terms having equivalenttechnical meanings may be used. Further, the present disclosure is notlimited by the following terms and designations and may be applied toother systems according to other standards in the same manner. Singularforms may include plural forms as well unless the context clearlyindicates otherwise.

FIG. 1 illustrates the configuration of a wireless communication systemaccording to an exemplary embodiment of the present disclosure. In FIG.1, a transmission apparatus 100 may be a base station or a terminal.Also, a reception apparatus 102 may be a base station or a terminal. Forexample, the transmission apparatus 100 may be a base station, and thereception apparatus 102 may be a terminal. Alternatively, thetransmission apparatus 100 may be a terminal, and the receptionapparatus may be a base station. In addition, both the transmissionapparatus 100 and the reception apparatus 102 may be terminals.

Referring to FIG. 1, the transmission apparatus 100 includes a pluralityof transmitting antennas. The transmission apparatus 100 transmits asignal to the reception apparatus 102 using the plurality oftransmitting antennas. In particular, the transmission apparatus 100according to the exemplary embodiment of the present disclosure maygenerate a signal (e.g., a reference signal) for the reception apparatus102 to estimate a channel (h) 110 using a Golay sequence generator 101and may transmit the generated signal to the reception apparatus 102.For example, the transmission apparatus 100 may generate a Golaysequence by performing a recursive procedure represented below byEquation 1 using the Golay sequence generator 101. The transmissionapparatus 100 may transmit a reference signal including the generatedGolay sequence to the reception apparatus 102. Here, the Golay sequencemay be included in a Channel Estimation Field (CEF) of the referencesignal.

A₀(k)=δ(k)

B ₀(k)=δ(k)

A _(n)(k)=W _(n) A _(n−1)(k)+B _(n−1)(k−D _(n))

B _(n)(k)=W _(n) A _(n−1)(k)−B _(n−1)(k−D _(n))  Equation 1

Here, n=1, 2, . . . , N, which may denote the number of iterations.Further, k=0, 1, . . . , 2N−1, and D_(n)=2^(Pn), which may denote adelay, where P_(n) may be a permutation of {0, 1, . . . , N}. W_(n) maybe an arbitrary complex number of unit magnitude. D_(n) and W_(n) maydenote seeds for generating a Golay sequence. A_(n)(k) and B_(n)(k) are0 where k<0, k≥2n. δ(k) may denote a delta function.

The transmission apparatus 100 may generate a Golay sequence based on Dnand Wn according to Equation 1. For example, the transmission apparatus100 may generate Golay sequences Ga₁₂₈(k)=A₇(128-k) andGb₁₂₈(k)=B₇(128-k), illustrated in FIG. 2, based on D_(n) and W_(n)represented by Equation 2.

D _(n)=[1,8,2,4,14,32,64]

W _(n)=[−1,−1,−1,−1,1,−1,−1]  Equation 2

The transmission apparatus 100 according to the exemplary embodiment ofthe present disclosure may generate and transmit a reference signal forminimizing a channel estimation error based on a Golay sequence. Forexample, the transmission apparatus 100 may generate different Golaysequences based on different seeds and may generate reference signalsincluding the different Golay sequences. Here, the transmissionapparatus 100 may transmit the generated reference signals to thereception apparatus 102 via different antennas. In another example, thetransmission apparatus 100 may generate a Golay sequence using aparticular seed and may transmit the same reference signals includingthe same Golay sequence via different antennas. Here, the transmissionapparatus 100 may control the reference signals to be transmitted atdifferent times. A method for the transmission apparatus 100 to generateand transmit a reference signal based on a Golay sequence according toan exemplary embodiment of the present disclosure will be described indetail below.

The reception apparatus 102 may include a plurality of receivingantennas. The reception apparatus 102 may receive a signal from thetransmission apparatus 100 using the plurality of receiving antennas. Inparticular, the reception apparatus 102 may include a Golay correlator103 and may estimate the channel (h) 110 between the transmissionapparatus 100 and the reception apparatus 102 using the Golay correlator103. Here, the Golay correlator 103 may be configured based on a Golaysequence generation method of the transmission apparatus 100. Therefore,a method for generating and transmitting a reference signal based on aGolay sequence may be preset in each of the transmission apparatus 100and the reception apparatus 102 or may be agreed upon between thetransmission apparatus 100 and the reception apparatus 102 via theexchange of signals.

FIGS. 3A and 3B illustrate a CEF including a Golay sequence. FIG. 3Aillustrates a CEF 300 for a system supporting a single carrier PHY(hereinafter referred to as a ‘SC PHY CEF’), and FIG. 3B illustrates aCEF 310 for an Orthogonal Frequency Division Multiplexing (OFDM) PHYsystem (hereinafter referred to as an ‘OFDM PHY CEF’). In FIGS. 3A and3B, a denotes Ga128, b denotes Gb128, u denotes Gu512, and v denotesGv512. Here, Ga128 denotes a Golay a sequence Ga₁₂₈(k) including 128samples illustrated in FIG. 2, and Gb128 denotes a Golay b sequenceGb₁₂₈(k) including 128 samples. Also, Gu512 and Gv512 respectivelydenote a Golay u sequence and a Golay v sequence, each of which includes512 samples. Here, Gu512 may include −Gb128, −Ga128, Gb128, and −Ga128in order, and Gv512 may include −Gb128, Ga128, −Gb128, −Ga128 in order.That is, each of the Golay u sequence and the Golay v sequence mayinclude the Golay a sequence and the Golay b sequence.

FIG. 4 illustrates an example of transmitting and receiving the CEF ofFIG. 3A in a wireless communication system.

Referring to FIG. 4, a transmission apparatus 100 transmits a referencesignal including the SC PHY CEF 300 illustrated in FIG. 3A to areception apparatus 102 via one antenna. Accordingly, the receptionapparatus 102 may receive one reference signal transmitted from thetransmission apparatus 100 via one antenna and may estimate a channelh₁. Here, the signal received by the reception apparatus 102 may berepresented by Equation 3.

y _(t) ₀ =h ₁ *u

y _(t) ₁ =h ₁ *v  Equation 3

Here, yt₀ denotes a signal received at time t₀, and yt₁ denotes a signalreceived at time t₁. h₁ denotes a channel between one antenna of thetransmission apparatus 100 and one antenna of the reception apparatus102. u denotes Gu512 that is a Golay u sequence including 512 samples,and v denotes Gv512 that is a Golay u sequence including 512 samples.

The reception apparatus 102 may input the received signal represented byEquation 3 into the Golay correlator 103, thereby obtaining a signalrepresented by Equation 4. The Golay correlator 103 may include Gu512and Gv512.

$\begin{matrix}{{R_{y_{t_{0}}u} = {h_{1}*R_{uu}}}{R_{y_{t_{1}}v} = {h_{1}*R_{vv}}}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Here, R_(yt0u) denotes a signal obtained by inputting a signal yt₀received at time t₀ into the Golay correlator 103, and R_(yt1v) denotesa signal obtained by inputting a signal yt₁ received at time t₁ into theGolay correlator 103.

The reception apparatus 102 may add the obtained signals represented byEquation 4, thereby obtaining a channel h₁ represented by Equation 5.

h ₁*(R _(uu) +R _(vv))=h ₁  Equation 5

For example, the reception apparatus 102 may estimate the channel h₁using the characteristics of Golay sequences Gu512 and Gv512 such thatR_(uu) and R_(vv) are impulse signals.

As described above in FIG. 4, the transmission apparatus 100 mayestimate a channel using the SC PHY CEF 300 of FIG. 3A or the OFDM PHYCEF 310 of FIG. 3B, which is suitable for SISO channel estimation. Thatis, the CEF transmission/reception scheme illustrated in FIGS. 3A, 3B,and 4 is not suitable for MIMO channel estimation. For example, when thetransmission apparatus 100 transmits the same CEF via a plurality ofantennas, the reception apparatus 102 cannot accurately estimate an MIMOchannel due to interaction between the same CEFs. Therefore, anexemplary embodiment of the present disclosure proposes a CEFtransmission/reception scheme capable of MIMO channel estimation in anMIMO system.

FIG. 5 illustrates an example of transmitting the CEFs illustrated inFIGS. 3A and 3B in a 2×2 MIMO system according to an exemplaryembodiment of the present disclosure. Although FIG. 5 shows only a firstreceiving antenna of a reception apparatus 102 for convenience, a secondreceiving antenna of the reception apparatus 102 may also be configuredin the same manner.

Referring to FIG. 5, a first transmitting antenna of a transmissionapparatus 100 transmits the SC PHY CEF 300 illustrated in FIG. 3A, and asecond transmitting antenna transmits the OFDM PHY CEF 310 illustratedin FIG. 3B. The SC PHY CEF 300 and the OFDM PHY CEF 310 transmitted fromthe transmission apparatus 100 pass through a channel h₁ and a channelh₂ and are received by a first receiving antenna of the receptionapparatus 102. The signals received by the reception apparatus 102 maybe represented by Equation 6.

y _(t) ₀ =h ₁ *u+h ₂ *v

y _(t) ₁ =h ₁ *v+h ₂ *u  Equation 6

Here, yt₀ denotes a signal received at time t₀, and yt₁ denotes a signalreceived at time t₁. h₁ denotes a channel between the first transmittingantenna of the transmission apparatus 100 and the first receivingantenna of the reception apparatus 102, and h₂ denotes a channel betweenthe second transmitting antenna of the transmission apparatus 100 andthe first receiving antenna of the reception apparatus 102. u denotesGu512 that is a Golay u sequence including 512 samples, and v denotesGv512 that is a Golay u sequence including 512 samples.

The reception apparatus 102 may input the received signal represented byEquation 6 into a Golay correlator 103, thereby obtaining a signalrepresented by Equation 7. The Golay correlator 103 may include Gu512and Gv512.

$\begin{matrix}{{R_{y_{t_{0}}u} = {{h_{1}*R_{uu}} + {h_{2}*R_{vu}}}}{R_{y_{t_{1}}u} = {{h_{1}*R_{vu}} + {h_{2}*R_{uu}}}}{R_{y_{t_{0}}v} = {{h_{1}*R_{uv}} + {h_{2}*R_{vv}}}}{R_{y_{t_{1}}v} = {{h_{1}*R_{vv}} + {h_{2}*R_{uv}}}}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

Here, R_(yt0u) and R_(yt0v) denote signals obtained by inputting asignal yt₀ received at time t₀ into the Golay correlator 103, andR_(yt1v) and R_(yt1u) denote signals obtained by inputting a signal yt₁received at time t₁ into the Golay correlator 103.

The reception apparatus 102 may add R_(yt0u) and R_(yt1v), and may addR_(yt1u) and R_(yt0v), thereby obtaining channels h₁ and h₂ according toEquation 8.

$\begin{matrix}{{{R_{y_{t_{0}}u} + R_{y_{t_{1}}v}} = {h_{1} + {h_{2}*\left( {R_{uv} + R_{vu}} \right)}}}{{R_{y_{t_{0}}v} + R_{y_{t_{1}}u}} = {h_{2} + {h_{1}*\left( {R_{uv} + R_{vu}} \right)}}}} & {{Equation}\mspace{14mu} 8}\end{matrix}$

Here, as illustrated in FIG. 6, in a channel measurement interval 600,R_(uv) is 0, but R_(vu) is not 0. Here, the channel measurement interval600 may include 63 samples. Therefore, when the reception apparatus 102estimates channel h₁ and h₂ according to Equation 8, a channelestimation error may occur due to R_(vu).

FIG. 7 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 5. FIG. 7 shows the Mean SquareError (MSE) according to Signal-to-Noise Ratio (SNR). In FIG. 7,Reference shows optimal performance. Further, XPD n (in dB, where n is4, 8, 12, 16, and 20) denotes the ratio of the size of h₁ to the size ofh₂. The estimation of h₁ by the reception apparatus 102 is affected byR_(vu) by the size of h₂. Therefore, referring to FIG. 7, the lower XPDis, the more MSE performance deteriorates. Particularly, an XPD of 4 dBhas an MSE value measured greater than that for an XPD of greater than 4dB. Thus, the following exemplary embodiment proposes a CEFtransmission/reception scheme in which channel estimation performancedoes not deteriorate even when XPD is low.

FIGS. 8A and 8B illustrate the configuration of a transmission signalfor channel estimation according to an exemplary embodiment of thepresent disclosure.

Referring to FIGS. 8A and 8B, a transmission apparatus 100 according tothe exemplary embodiment of the present disclosure may generate twodifferent CEFs and may transmit the CEFs through separate antennas. Forexample, the transmission apparatus 100 may generate a first CEF 800 anda second CEF 810 illustrated in FIG. 8A, or may generate a first CEF 800and a second CEF 820 illustrated in FIG. 8B. For example, depending onthe channel measurement interval prediction method, the first CEF andthe second CEF may be generated illustrated in FIG. 8A, or the first CEFand the second CEF may be generated illustrated in FIG. 8B.

Referring to FIG. 8A, the first CEF 800 may include −a, u, v, and −b,like the CEF 300 of FIG. 3A, and the second CEF 810 may include −a,u⁽¹⁾, v⁽¹⁾, and −b⁽¹⁾. Referring to FIG. 8B, the first CEF 800 mayinclude −a, u, v, and −b, like the CEF 300 of FIG. 3A, and the secondCEF 820 may include −a⁽¹⁾, u⁽¹⁾, v⁽¹⁾, and −b⁽¹⁾. Here, u⁽¹⁾ denotesG⁽¹⁾u512, and G⁽¹⁾u512 includes −b⁽¹⁾, −a⁽¹⁾, b⁽¹⁾, and −a⁽¹⁾ in order.Further, v⁽¹⁾ denotes G⁽¹⁾v512, and G⁽¹⁾v512 includes −b⁽¹⁾, a⁽¹⁾,−b⁽¹⁾, and −a⁽¹⁾ in order. Here, a⁽¹⁾ and b⁽¹⁾ may be obtained based onDn and Wn represented by Equation 9.

D _(n)=[1,8,2,4,16,32,64]

W _(n)=[1,−1,−1,−1,1−1,−1]

For example, a and b respectively denote Ga₁₂₈(k) and Gb₁₂₈(k) obtainedby applying Dn and Wn in Equation 2 to Equation 1, and a⁽¹⁾ and b⁽¹⁾respectively denote G^((1)a) ₁₂₈(k) and G⁽¹⁾b₁₂₈(k) obtained by applyingDn and Wn in Equation 9 to Equation 1. Here, Wn in Equation 2 and Wn inEquation 9 are different, while Dn in Equation 2 and Dn in Equation 9are the same. Using the same Dn in Equation 2 and Equation 9 is forconvenience in implementing a correlator. Therefore, Dn in Equation 2and Dn in Equation 9 may be set to be different depending on the designmethod.

FIG. 9 illustrates an example of transmitting the CEFs of FIG. 8Aaccording to an exemplary embodiment of the present disclosure. Here, inFIG. 9, a 2×2 MIMO system is assumed, but only a first receiving antennaof a reception apparatus 102 is shown for convenience. However, a secondreceiving antenna of the reception apparatus 102 may also be configuredin the same manner. Although FIG. 9 illustrates a case of transmittingand receiving the first CEF and the second CEF of FIG. 8A, the first CEFand the second CEF of FIG. 8B may be transmitted and received in thesame manner.

Referring to FIG. 9, a Golay sequence generator 101 of a transmissionapparatus 100 generates a first CEF 800 and a second CEF 810, asillustrated in FIG. 8A. The transmission apparatus 100 transmits thefirst CEF 800 through a first transmitting antenna and transmits thesecond CEF 810 through a second transmitting antenna. The first CEF 800and the second CEF 810 transmitted from the transmission apparatus 100pass through a channel h₁ and a channel h₂ and are received by the firstreceiving antenna of the reception apparatus 102. The signals receivedby the reception apparatus 102 may be represented by Equation 10.

y _(t) ₀ =h ₁ *u+h ₂ *u ⁽¹⁾

y _(t) ₁ =h ₁ *v+h ₂ *v ⁽¹⁾  Equation 10

Here, yt₀ denotes a signal received at time t₀, and yt₁ denotes a signalreceived at time t₁. h₁ denotes a channel between the first transmittingantenna of the transmission apparatus 100 and the first receivingantenna of the reception apparatus 102, and h₂ denotes a channel betweenthe second transmitting antenna of the transmission apparatus 100 andthe first receiving antenna of the reception apparatus 102. u denotesGu512, v denotes Gv512, u⁽¹⁾ denotes G⁽¹⁾u512, and v⁽¹⁾ denotesG⁽¹⁾v512.

The reception apparatus 102 may input the received signal represented byEquation 10 into a first Golay correlator 103-1 and a second Golaycorrelator 103-2, thereby obtaining a signal represented by Equation 11.The first Golay correlator 103-1 may include G⁽¹⁾u512 and G⁽¹⁾v512, andthe second Golay correlator 103-2 may include Gu512 and Gv512.

$\begin{matrix}{{R_{y_{t_{0}}u} = {{h_{1}*R_{uu}} + {h_{2}*R_{u^{(1)}u}}}}{R_{y_{t_{1}}v} = {{h_{1}*R_{vv}} + {h_{2}*R_{v^{(1)}v}}}}{R_{y_{t_{0}}u^{(1)}} = {{h_{1}*R_{{uu}^{(1)}}} + {h_{2}*R_{u^{(1)}u^{(1)}}}}}{R_{y_{t_{1}}v^{(1)}} = {{h_{1}*R_{{vv}^{(1)}}} + {h_{2}*R_{v^{(1)}v^{(1)}}}}}} & {{Equation}\mspace{14mu} 11}\end{matrix}$

Here, R_(yt0u) ⁽¹⁾ and R_(yt0u) denote signals obtained by inputting asignal yt₀ received at time t₀ into the first Golay correlator 103-1 andthe second Golay correlator 103-2, and R_(yt1v) ⁽¹⁾ and R_(yt1v) denotesignals obtained by inputting a signal yt₁ received at time t₁ into thefirst Golay correlator 103-1 and the second Golay correlator 103-2.

The reception apparatus 102 may add R_(yt0u) ⁽¹⁾ and R_(yt1v) ⁽¹⁾ andmay add R_(yt0u) and R_(yt1v), thereby estimating channels h₁ and h₂according to Equation 12.

h ₁ +h ₂*(R _(v) _(v) +R _(u) _(u))

h ₂ +h ₁*(R _(vv) ₍₁₎ +R _(uu) ₍₁₎ )  Equation 12

Here, as illustrated in FIG. 10, in a channel measurement interval 1000,R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾, R_(v) ⁽¹⁾ _(v), and R_(u) ⁽¹⁾ _(u) are 0. Thechannel measurement interval 1000 may include 63 samples. Therefore,when the reception apparatus 102 estimates the channel h₁ and h₂according to Equation 12, no channel estimation error occurs. Here, asin FIG. 10, R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾, Rv⁽¹⁾v, and Ru⁽¹⁾u are 0 in thechannel measurement interval 1000, because u⁽¹⁾ has an internal signopposite to that of v−1, which is reversed v, and v⁽¹⁾ has an internalsign opposite to that of u−1, which is reversed u. For example, v−1 mayinclude −a−1, −b−1, a−1, and −b−1; and v−1 in u⁽¹⁾ may include a−1,−b−1, −a−1, −b−1. Further, u−1 may include −a−1, b−1, −a−1, and −b−1;and v−1 v⁽¹⁾ in may include a−1, b−1, a−1, and −b−1.

Only Wn illustrated in Equation 9 may make R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾,Rv⁽¹⁾v, and Ru⁽¹⁾u be 0 in the channel measurement interval 1000 in FIG.10. For example, referring to channel estimation errors by seedillustrated in FIG. 11, a channel estimation error of an eighteenth seedamong 128 seeds W_(n) has a remarkably lower MSE value than those ofother seeds, which indicates that interference components may beeliminated or minimized in channel estimation using sequences based onthe eighteenth seed. Referring to FIG. 10, among the 128 seeds W_(n) forgenerating a Golay sequence, only the eighteenth seed W_(n) illustratedin Equation 9 has a characteristic of making R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾,Rv⁽¹⁾v, and Ru⁽¹⁾u be 0 in the channel measurement interval 1000.

In some exemplary embodiments, the transmission apparatus 100 may selecttwo seeds W_(n) from among a plurality of seeds Wn for generating aGolay sequence such that R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾, Rv⁽¹⁾v, and Ru⁽¹⁾u are0. For example, the transmission apparatus 100 may select W_(n) inEquation 2 and W_(n) in Equation 9 from among the 128 seeds W_(n). Thereception apparatus 102 may receive sequences generated based on W_(n)in Equation 2 and W_(n) in Equation 9, thereby eliminating interferencecomponents through u⁽¹⁾ and v⁽¹⁾.

In some other exemplary embodiments, the transmission apparatus 100 mayselect two seeds from among a plurality of seeds D_(n) for generating aGolay sequence such that R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾, Rv⁽¹⁾v, and Ru⁽¹⁾u are0. In some other exemplary embodiments, the transmission apparatus 100may select combinations of two seeds from among combinations of aplurality of seeds D_(n) and W_(n) for generating a Golay sequence suchthat R_(vv) ⁽¹⁾, R_(uu) ⁽¹⁾, Rv⁽¹⁾v, and Ru⁽¹⁾u are 0.

Seeds D_(n), seeds W_(n), or combinations thereof to minimizeinterference components of the reception apparatus 102 may be obtainedvia a simulation or experimental result or may be determined to satisfya particular relational equation. For example, the transmissionapparatus 100 may determine a seed to generate a Golay v sequence inwhich at least some components have a sign opposite to that of somecomponents in the reverse of a Golay u sequence determined based onanother seed. In another example, the transmission apparatus 100 maydetermine a seed to generate a Golay u sequence in which at least somecomponents have a sign opposite to that of some components in thereverse of a Golay v sequence determined based on another seed.

FIG. 12 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 9. FIG. 12 shows the MSE accordingto SNR. In FIG. 12, Reference shows optimal performance. Further, XPD n(in dB, where n is 4, 8, 12, 16, and 20) denotes the ratio of the sizeof h₁ to the size of h₂. FIG. 12 shows that MSE performance is similarto the performance of Reference regardless of the XPD value. Althoughthere is a slight difference between the MSE value of XPD 4 and theperformance of Reference, the desired strength of a signal at the sameSNR is reduced due to interference, and thus the MSE difference betweenXPD and Reference is not regarded as performance deterioration.According to various exemplary embodiments of the present disclosure,the transmission apparatus 100 may perform transmission by delaying thesecond antenna by 36.48 ns or shorter in order to improve overall frameperformance.

As shown in FIG. 9, when a channel is estimated by transmitting andreceiving the first CEF and the second CEF based on the CEFs shown inFIGS. 8A and 8B, the reception apparatus 102 needs two correlators foreach receiving antenna. However, in the exemplary embodiment of thepresent disclosure, a correlator may be reused in terms of time, andthus one correlator may be included for each antenna, which will bedescribed in detail below with reference to FIG. 13.

FIG. 13 illustrates the structure of a reception apparatus in which asingle correlator is used for each antenna according to an exemplaryembodiment of the present disclosure. FIG. 13 shows a case where atransmission apparatus 100 transmits a reference signal including afirst CEF 800 via a first antenna and transmits a reference signalincluding a second CEF 810 via a second antenna. Further, it is assumedthat the reception apparatus 102 includes a first receiving antenna anda second receiving antenna in a 2×2 MIMO system. However, the samestructure of the reception apparatus 102 illustrated in FIG. 13 may beapplied to a reception apparatus 102 supporting an N×N MIMO system or anN×M MIMO system.

Referring to FIG. 13, the reception apparatus 102 may include a firstGolay correlator 103-1 and a second Golay correlator 103-2. Here, thefirst Golay correlator 103-1 may be configured using G⁽¹⁾u512 andG⁽¹⁾v512, and the second Golay correlator 103-2 may be configured usingGu512 and Gv512.

At time t₀, the reception apparatus 102 may provide a signal receivedvia the first receiving antenna to the second Golay correlator 103-2 andmay provide a signal received via the second receiving antenna to thefirst Golay correlator 103-1, thereby obtaining R_(u) and R_(u) ⁽¹⁾.R_(u) and R_(u) ⁽¹⁾ are similar to R_(yt0u) and R_(yt0u) ⁽¹⁾ illustratedin Equation 11. Here, it is assumed that the reception apparatus 102 canpredict a channel measurement interval using R_(u) and R_(u) ⁽¹⁾ beforetime t₀. The reception apparatus 102 may delay obtained R_(u) and R_(u)⁽¹⁾ for 292 ns. Here, 292 ns corresponds to 512 samples.

At time t₁ after 292 ns from time t₀, the reception apparatus 102 mayprovide a signal received via the first receiving antenna to the secondGolay correlator 103-2 and may provide a signal received via the secondreceiving antenna to the first Golay correlator 103-1, thereby obtainingR_(v) and R_(v) ⁽¹⁾. R_(v) and R_(v) ⁽¹⁾ are similar to R_(yt1v) andR_(yt1v) ⁽¹⁾ illustrated in Equation 11.

The reception apparatus 102 may add R_(u) obtained at time t₀ and R_(v)obtained at time t₁ and may add Ru⁽¹⁾ obtained at time t₀ and Rv⁽¹⁾obtained at time t₁, thereby obtaining h₁₁ and h₂₂.

The reception apparatus 102 may store, in a buffer, the signals receivedat time t₀ via the first receiving antenna and the second receivingantenna. At time t₂ after 438 ns from time t₁, the reception apparatus102 provides the signal received via the first receiving antenna andstored in the buffer to the first Golay correlator 103-1 and providesthe signal received via the second receiving antenna and stored in thebuffer to the second Golay correlator 103-2. Accordingly, the receptionapparatus 102 may obtain R_(u) ⁽¹⁾ and R_(u). Here, Ru⁽¹⁾ and Ru aresimilar to R_(yt0u) ⁽¹⁾ and R_(yt0u) illustrated in Equation 11. Thereception apparatus 102 may delay obtained R_(u) ⁽¹⁾ and R_(u) for 292ns. Here, 292 ns corresponds to 512 samples.

At time t₃ after 292 ns from time t₂, the reception apparatus 102 mayprovide a signal received via the first receiving antenna to the firstGolay correlator 103-1 and may provide a signal received via the secondreceiving antenna to the second Golay correlator 103-2, therebyobtaining R_(v) ⁽¹⁾ and R_(v). Here, Rv⁽¹⁾ and R_(v) are similar toR_(yt1v) ⁽¹⁾ and R_(yt1v) illustrated in Equation 11.

The reception apparatus 102 may add R_(u) obtained at time t₂ and R_(v)obtained at time t₃ and may add R_(u) ⁽¹⁾ obtained at time t₂ and R_(v)⁽¹⁾ obtained at time t₃, thereby obtaining h₂1 and h₁2.

As described above, when one Golay correlator is included for eachantenna, the reception apparatus 102 may buffer a received signal andmay use the Golay correlator for each antenna in a shifted manner,thereby estimating an MIMO channel. However, when one Golay correlatoris included for each antenna, the reception apparatus 102 may need abuffer to buffer a received signal for each antenna or a delay element.

FIG. 14 illustrates the configuration of a transmission signal forchannel estimation according to another exemplary embodiment of thepresent disclosure.

Referring to FIG. 14, a transmission apparatus 100 according to theexemplary embodiment of the present disclosure may generate twoidentical CEFs and may transmit the two identical CEFs via individualantennas at different times. For example, the transmission apparatus 100may generate a first CEF 1400 and a second CEF 1410. The first CEF 1400and the second CEF 1410 may include the same Golay sequence. That is,the first CEF 1400 may include −a, u, v, and −b like the CEF 300 of FIG.3A, and the second CEF 1410 may also include −a, u, v, and −b like theCEF 300 of FIG. 3A. However, in the exemplary embodiment of the presentdisclosure, the transmission time of the second CEF 1410 is configuredto be delayed by a predetermined time 1420 from the transmission time ofthe first CEF 1400. For example, the second CEF may be transmitted in acyclic-shifter manner after the first CEF is transmitted. Here, thepredetermined time 1420 may change according to the design method. Forexample, the predetermined time may be equal to or longer than 36.48 ns,which corresponds to 64 samples.

FIG. 15 illustrates an example of transmitting the CEFs of FIG. 14according to an exemplary embodiment of the present disclosure. Here, inFIG. 15, a 2×2 MIMO system is assumed, but only a first receivingantenna of a reception apparatus 102 is shown for convenience. However,a second receiving antenna of the reception apparatus 102 may also beconfigured in the same manner.

Referring to FIG. 15, a Golay sequence generator 101 of the transmissionapparatus 100 generates a first CEF 1400 and a second CEF 1410, asillustrated in FIG. 14. The transmission apparatus 100 transmits thefirst CEF 1400 via a first transmitting antenna and transmits the secondCEF 1410 via a second transmitting antenna. Here, the transmissionapparatus 100 controls the second CEF 1410 to be transmitted at a timedelayed by a predetermined time (for example, 36.48 ns) from thetransmission time of the first CEF 1400. The first CEF 1400 and thesecond CEF 1410 transmitted from the transmission apparatus 100 passthrough a channel h₁ and a channel h₂ and are received by the firstreceiving antenna of the reception apparatus 102. The signals receivedby the reception apparatus 102 may be represented by Equation 13.

y _(t) ₀ =h ₁ *u+h ₂ *u _(d−)

y _(t) ₁ =h ₁ *u _(d+) +h ₂ *u

y _(t) ₂ =h ₁ *v+h ₂ *v _(d−)

y _(t) ₃ =h ₁ *v _(d+) +h ₂ *v  Equation 13

Here, yt₀ denotes a signal received at time t₀, yt₂ denotes a signalreceived at time t₂, yt₁ denotes a signal received at time t₁, and yt₃denotes a signal received at time t₃. Further, u_(d−) and v_(d−)respectively denote signals u and v delayed by a predetermined time (forexample, 36.48 ns), and u_(d+) and v₊ respectively denote signals u andv transmitted by the predetermined time before. For example, ud− mayindicate that a Golay sequence u is received with a delay of apredetermined time from a corresponding time, and ud+ may indicate thata Golay sequence u is received by a predetermined time before thecorresponding time. h₁ denotes a channel between the first transmittingantenna of the transmission apparatus 100 and the first receivingantenna of the reception apparatus 102, and h₂ denotes a channel betweenthe second transmitting antenna of the transmission apparatus 100 andthe first receiving antenna of the reception apparatus 102. u denotesGu512, and v denotes Gv512.

The reception apparatus 102 may input the received signal represented byEquation 13 to a first Golay correlator 103-2 and a second Golaycorrelator 103-2, thereby obtaining a signal represented by Equation 14.The first Golay correlator 103-2 may include Gu512 and Gv512, and thesecond Golay correlator 103-2 may also include Gu512 and Gv512. That is,the reception apparatus 102 includes two identical Golay correlators103-2, but the two Golay correlators 103-2 are referred to as a firstGolay correlator 103-2 and a second Golay correlator 103-2,respectively, for convenience of explanation.

$\begin{matrix}{{R_{y_{t_{0}}u} = {{h_{1}*R_{uu}} + {h_{2}*R_{u_{d -}u}}}}{R_{y_{t_{1}}u} = {{h_{1}*R_{u_{d +}u}} + {h_{2}*R_{uu}}}}{R_{y_{t_{2}}v} = {{h_{1}*R_{vv}} + {h_{2}*R_{v_{d -}v}}}}{R_{y_{t_{3}}v} = {{h_{1}*R_{v_{d +}v}} + {h_{2}*R_{vv}}}}} & {{Equation}\mspace{14mu} 14}\end{matrix}$

Here, R_(yt0u) denotes a signal obtained by inputting a signal yt₀received at time t₀ into the first Golay correlator 103-2, and R_(yt1u)denotes a signal obtained by inputting a signal y_(t1) received at timet₁ into the second Golay correlator 103-2. Further, R_(yt2v) denotes asignal obtained by inputting a signal yt₂ received at time t₂ into thefirst Golay correlator 103-2, and R_(yt3v) denotes a signal obtained byinputting a signal yt₃ received at time t₃ into the second Golaycorrelator 103-2.

The reception apparatus 102 may add R_(yt0u) and R_(yt2v) and may addR_(yt1u) and R_(yt3v), thereby estimating channels h₁ and h₂ accordingto Equation 15.

h ₁ +h ₂*(R _(v) _(d−) _(v) +R _(u) _(d−) _(u))

h ₂ +h ₁*(R _(v) _(d+) _(v) +R _(u) _(d+u) _(u))  Equation 15

Here, R_(vd−v), R_(ud−u), R_(vd+v), and R_(ud+u) are 0 in a channelmeasurement interval. The channel measurement interval may include 63samples. Therefore, when the reception apparatus 102 estimates thechannel h₁ and h₂ according to Equation 15, no channel estimation erroroccurs. Here, R_(vd−v), R_(ud−u), R_(vd+v), and R_(ud+a) are 0 in thechannel measurement interval 1000, because neighbors of a correlationpeak are 0 due to the periodic characteristics of the Golay sequences uand v.

FIG. 16 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 15. FIG. 16 shows the MSEaccording to SNR. In FIG. 16, Reference shows optimal performance.Further, XPD n (in dB, where n is 4, 8, 12, 16, and 20) denotes theratio of the size of h₁ to the size of h₂. FIG. 16 shows that MSEperformance is similar to the performance of Reference regardless of theXPD value. Although there is a slight difference between the MSE valueof XPD 4 and the performance of Reference, the desired strength of asignal at the same SNR is reduced due to interference, and thus the MSEdifference between XPD and Reference is not regarded as performancedeterioration.

The CEF transmission/reception schemes for a 2×2 MIMO system have beenillustrated in the foregoing description. Hereinafter, a CEFtransmission/reception scheme for a 4×4 MIMO system will be describedwith reference to examples.

FIGS. 17A and 17B illustrate the configuration of a transmission signalfor channel estimation according to various exemplary embodiments of thepresent disclosure.

Referring to FIGS. 17A and 17B, a transmission apparatus 100 accordingto the exemplary embodiment of the present disclosure may generate fourdifferent CEFs and may transmit each CEF via each antenna. For example,the transmission apparatus 100 may generate a first CEF 1700, a secondCEF 1710, a third CEF 1720, and a fourth CEF 1730 as illustrated in FIG.17A, or may generate a first CEF 1700, a second CEF 1740, a third CEF1750, and a fourth CEF 1760 as illustrated in FIG. 17B. For example,according to the channel measurement interval prediction method, thetransmission apparatus 100 may generate the first to fourth CEFs asillustrated in FIG. 17A or may generate the first to fourth CEFs asillustrated in FIG. 17B. Here, the CEFs of FIGS. 17A and 17B may bedivided into a first section and a second section. The CEFs of FIGS. 17Aand 17B are configured such that a Golay sequence is transmitted throughone of the first section and the second section.

Referring to FIG. 17A, a first section of the first CEF 1700 may include−a, u, v, and −b like the first CEF 800 of FIG. 8A, and a second sectionthereof includes no Golay sequence. A first section of the second CEF1710 may include −a, u⁽¹⁾, v⁽¹⁾, and −b⁽¹⁾ like the second CEF 810 ofFIG. 8A, and a second section thereof includes no Golay sequence. Afirst section of the third CEF 1720 may include only −a at the head forsynchronization, and a second section thereof may include −a⁽¹⁾, u, v,and −b. Here, the second section of the third CEF 1720 starts with −a⁽¹⁾to be distinguished from the first section of the first CEF 1700. Afirst section of the fourth CEF 1730 may include only −a at the head forsynchronization, and a second section thereof may include −1 ⁽¹⁾, u⁽¹⁾,v⁽¹⁾, and −b⁽¹⁾. Here, the second section of the fourth CEF 1730 startswith −a⁽¹⁾ to be distinguished from the first section of the second CEF1710.

Referring to FIG. 17B, a first section of the first CEF 1700 may include−a, u, v, and −b like the first CEF 800 of FIG. 8A, and a second sectionthereof includes no Golay sequence. A first section of the second CEF1740 may include −a⁽¹⁾, u⁽¹⁾, v⁽¹⁾, and −b⁽¹⁾ like the second CEF 810 ofFIG. 8B, and a second section thereof includes no Golay sequence. Afirst section of the third CEF 1750 may include only −a at the head forsynchronization, and a second section thereof may include −a, u, v, and−b like the first section of the first CEF 1700. A first section of thefourth CEF 1760 may include only −a at the head for synchronization, anda second section thereof may include −a⁽¹⁾, u⁽¹⁾, v⁽¹⁾, and −b⁽¹⁾ likethe first section of the second CEF 1740.

Referring to FIGS. 17A and 17B, a first antenna of transmissionapparatus 100 transmits the first CEFs 1700, and a second antennatransmits the second CEFs 1710 and 1740. Since the first CEFs 1700 andthe second CEFs 1710 and 1740 include a Golay sequence only in the firstsection, the first antenna and the second antenna transmit a signal onlyduring the first section and do not transmit a signal during the secondsection.

A third antenna of the transmission apparatus 100 transmits the thirdCEFs 1720 and 1750, and a fourth antenna transmits the fourth CEFs 1730and 1760. The third CEFs 1720 and 1750 and the fourth CEFs 1730 and 1760include a Golay sequence −a at the beginning in the first section andinclude a Golay sequence in the second section. Therefore, while thesignals of the first sections are transmitted through the first antennaand the second antenna, the third antenna and the fourth antenna of thetransmission apparatus 100 transmit only −a at the beginning and do nottransmit any more signals until the first sections terminate. The thirdantenna and the fourth antenna of the transmission apparatus 100transmit signals during the second sections in which the first antennaand the second antenna do not transmit any signal.

Therefore, the transmission signals of the first antenna and the secondantenna do not interfere in the transmission signals of the thirdantenna and the fourth antenna, and the transmission signals of thethird antenna and the fourth antenna do not interfere in thetransmission signals of the first antenna and the second antenna. Inthis case, a reception apparatus 102 may first receive the transmissionsignals from the first antenna and the second antenna of thetransmission apparatus 100 and may estimate a channel in the same manneras the CEF reception schemes illustrated in FIGS. 9 and 13. Then, thereception apparatus 102 may receive the transmission signals from thethird antenna and the fourth antenna and may estimate a channel in thesame manner as the CEF reception schemes illustrated in FIGS. 9 and 13.

FIG. 18 illustrates the structure of a reception apparatus that receivesthe CEF signal of FIG. 17A and estimates a channel. FIG. 18 shows thestructure of the reception apparatus 102 for estimating a channel whentwo Golay correlators 103-1 and 103-2 are included for each receivingantenna.

Referring to FIG. 18, the reception apparatus 102 may include a firstGolay correlator 103-1 and a second Golay correlator 103-2 for eachreceiving antenna. Here, the first Golay correlator 103-1 may beconfigured with G⁽¹⁾u512 and G⁽¹⁾v512, and the second Golay correlator103-2 may be configured with Gu512 and Gv512. With this structure, thereception apparatus 102 may obtain R_(u) and R_(u) ⁽¹⁾ at time t₀ andmay obtain R_(v) and R_(v) ⁽¹⁾ at time t₁ after 292 ns from time t₀,using a signal received from an i-th antenna. The reception apparatus102 may add R_(u) obtained at time t₀ and Rv obtained at time t₁ and mayadd R_(u) ⁽¹⁾ obtained at time t₀ and R_(v) ⁽¹⁾ obtained at time t₁,thereby estimating channels h_(i1) and h_(i2). Here, it is assumed thatthe reception apparatus 102 can predict a channel measurement intervalusing R_(u) and R_(u) ⁽¹⁾ before time t₀. Further, the receptionapparatus 102 may obtain R_(u) and R_(u) ⁽¹⁾ at time t₂ (t₂=t₁+438 ns)and may obtain R_(v) and R_(v) ⁽¹⁾ at time t₃ after 292 ns from time t₂,using a signal received from the i-th antenna. The reception apparatus102 may add Ru obtained at time t₂ and R_(v) obtained at time t₃ and mayadd R_(u) ⁽¹⁾ obtained at time t₂ and R_(v) ⁽¹⁾ obtained at time t₃,thereby estimating channels hi3 and hi4.

FIG. 19 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 18. FIG. 19 shows the MSEaccording to SNR. In FIG. 19, Reference shows optimal performance.Further, XPD n (in dB, where n is 4, 8, 12, 16, and 20) denotes theratio of the size of h₁ to the size of h₂. FIG. 19 shows that MSEperformance of XPDs other than XPD 4 is similar to that of Reference.Although the MSE performance of XPD 4 is about 1.5 dB lower than that ofReference, the desired strength of a signal at the same SNR is reduceddue to interference, and thus the MSE difference between XPD 4 andReference is not regarded as performance deterioration.

FIGS. 20A and 20B illustrate the configuration of a transmission signalfor channel estimation according to various exemplary embodiments of thepresent disclosure. Here, a method of using the transmission signalconfiguration method of FIG. 8 and the transmission signal configurationmethod of FIG. 14 together for a 4×4 MIMO system is shown.

Referring to FIGS. 20A and 20B, a transmission apparatus 100 accordingto the exemplary embodiment of the present disclosure may generate atleast two different CEFs and may transmit each CEF via each antenna. Forexample, the transmission apparatus 100 may generate and transmit afirst CEF 2000 to a fourth CEF 2030 as illustrated in FIG. 20A, or maygenerate and transmit a first CEF 2000 to a fourth CEF 2060 asillustrated in FIG. 20B. For example, according to the channelmeasurement interval prediction method, the first to fourth CEFs may beused as illustrated in FIG. 20A, or the first to fourth CEFs may be usedas illustrated in FIG. 20B.

Referring to FIG. 20A, the first CEF 2000 may include −a, u, v, and −b,like the first CEF 800 of FIG. 8B, and the second CEF 2010 may include−a⁽¹⁾, u⁽¹⁾, v⁽¹⁾, and −b⁽¹⁾, like the second CEF 820 of FIG. 8B.Further, the third CEF 2020 may be configured the same as the first CEF2000, and the fourth CEF may be configured the same as the second CEF2010. Here, the transmission time of the third CEF 2020 and the fourthCEF 2030 may be configured to be delayed by a predetermined time (forexample, 36.48 ns) from the transmission time of the first CEF 2000 andthe second CEF 2010. Here, the predetermined time may change accordingto the design method.

Referring to FIG. 20B, the first CEF 2000 may include −a, u, v, and −b,like the first CEF 800 of FIG. 8A, and the second CEF 2040 may include−a, u⁽¹⁾, v⁽¹⁾, and −b⁽¹⁾, like the second CEF 810 of FIG. 8A. Further,the third CEF 2050 may include −a⁽¹⁾, u, v, and −b, and the fourth CEFmay be configured the same as the second CEF 820 of FIG. 8B. Here, thetransmission time of the third CEF 2050 and the fourth CEF 2060 may beconfigured to be delayed by a predetermined time (for example, 36.48 ns)from the transmission time of the first CEF 2000 and the second CEF2040. Here, the predetermined time may change according to the designmethod.

Referring to FIGS. 20A and 20B, the transmission apparatus 100 maytransmit the first CEFs 2000 and the second CEFs 2010 and 2040respectively through a first antenna and a second antenna at a firsttime, and may transmit the third CEFs 2020 and 2050 and the fourth CEFs2030 and 2060 respectively through a third antenna and a fourth antennaat a second time after a predetermined time (for example, 36.48 ns) fromthe first time. According to various exemplary embodiments of thepresent disclosure, the transmission apparatus 100 may transmittransmission signals of the second antenna and the fourth antenna withrespective delays of 36.48 ns and 72.96 ns or shorter in order toimprove overall frame performance.

FIG. 21 illustrates an example of transmitting the CEFs of FIG. 20Baccording to various exemplary embodiments of the present disclosure.Here, in FIG. 21, a 4×4 MIMO system is assumed, but only a firstreceiving antenna of a reception apparatus 102 is shown for convenience.However, a second receiving antenna, a third receiving antenna, and/or afourth receiving antenna of the reception apparatus 102 may also beconfigured in the same manner. Although FIG. 21 illustrates a case oftransmitting and receiving the first CEF to the fourth CEF in FIG. 20B,the first CEF to the fourth CEF of FIG. 20A may be transmitted andreceived in the same manner.

Referring to FIG. 21, a Golay sequence generator 101 of a transmissionapparatus 100 generates a first CEF 2000, a second CEF 2040, a third CEF2050, and a fourth CEF 2060, as illustrated in FIG. 20B. Thetransmission apparatus 100 transmits the first CEF 2000 via a firsttransmitting antenna and transmits the second CEF 2040 via a secondtransmitting antenna at a first time. Then, the transmission apparatus100 transmits the third CEF 2050 via the third transmitting antenna andtransmits the fourth CEF 2060 via a fourth transmitting antenna at asecond time after a predetermined time from the first time.

The first CEF 2000, the second CEF 2040, the third CEF 2050, and thefourth CEF 2060 transmitted from the transmission apparatus 100 passthrough channels h₁, h₂, h₃, and h₄, respectively, and are received bythe first receiving antenna of the reception apparatus 102. Thereception apparatus 102 may input the signals received at time t₀ andtime t₁ to a first Golay correlator 103-1 and a second Golay correlator103-2, thereby obtaining a signal represented by Equation 16. The firstGolay correlator 103-1 may include G⁽¹⁾u512 and G⁽¹⁾v512, and the secondGolay correlator 103-2 may include Gu512 and Gv512.

$\begin{matrix}{\mspace{20mu} {R_{y_{t_{1}}v} = {{h_{1}*R_{vv}} + {h_{2}*R_{v^{(1)}v}} + {h_{3}*R_{v_{d -}v}} + {h_{4}*R_{v_{d -}^{(1)}v}}}}} & {{Equation}\mspace{14mu} 16} \\{R_{y_{t_{0}}u} = {{h_{1}*R_{uu}} + {h_{2}*R_{u^{(1)}u}} + {h_{3}*R_{u_{d -}u}} + {h_{4}*R_{u_{d -}^{(1)}u}}}} & \;\end{matrix}$

The reception apparatus 102 may add R_(yt0u) and R_(yt1v), therebyestimating a channel h₁ according to Equation 17.

$\begin{matrix}{h_{1} + {h_{2}*\left( {R_{v^{(1)}v} + R_{u^{(1)}u}} \right)} + {h_{3}*\left( {R_{v_{d -}v} + R_{u_{d -}u}} \right)} + {h_{4}*\left( {R_{v_{d -}^{(1)}v} + R_{u_{d -}^{(1)}u}} \right)}} & {{Equation}\mspace{14mu} 17}\end{matrix}$

Here, among all reference components illustrated in Equation 17,reference components other than Rud−u are 0 in a channel measurementinterval. For example, Rv⁽¹⁾v, Ru⁽¹⁾u, Rvd−v, Rvd−⁽¹⁾v, and Rud−⁽¹⁾u are0 in the channel measurement interval. The channel measurement intervalmay include 63 samples. Here, Rud−u is not 0, because the periodiccharacteristics of the Golay sequences in the CEFs of FIG. 20B arebroken. Therefore, when the reception apparatus 102 estimates a channel,a channel estimation error may occur due to Rud−u.

FIG. 22 shows a graph illustrating a channel estimation error in the CEFtransmission/reception scheme of FIG. 21. FIG. 22 shows the MSEaccording to SNR. In FIG. 22, Reference shows optimal performance.Further, XPD n (in dB, where n is 4, 8, 12, 16, and 20) denotes theratio of the size of h₁ to the size of h₂. FIG. 22 shows that MSEperformance of XPD 4 is slightly lower than that MSE performance of XPD4 in FIG. 19. However, the MSE performance of cases other than XPD 4 issimilar to the performance of Reference.

FIGS. 21 and 22 illustrate a channel estimation error that may occur inthe transmission and reception of the CEFs of FIG. 20B. According tovarious exemplary embodiments of the present disclosure, when thetransmission apparatus 100 transmits the CEFs of FIG. 20A, the receptionapparatus 102 may estimate a channel without any channel estimationerror, which is because the periodic characteristics of the Golaysequences in the CEFs of FIG. 20A are not broken, and all interferencecomponents are 0 in the channel measurement interval. Therefore, whenthe transmission apparatus 100 transmits the CEFs of FIG. 20A, a channelestimation error may be represented as illustrated in FIG. 19.

FIG. 23 illustrates the structure of a reception apparatus that receivesthe CEFs in FIG. 20A or FIG. 20B and estimates a channel.

FIG. 23 shows the structure of the reception apparatus 102 forestimating a channel when four Golay correlators are included for eachreceiving antenna.

Referring to FIG. 23, the reception apparatus 102 may include, for eachreceiving antenna, two Golay correlators using G⁽¹⁾u512 and G⁽¹⁾v512 andtwo Golay correlators using Gu512 and Gv512. With this structure, thereception apparatus 102 may obtain R_(u) and R_(u) ⁽¹⁾ at time t₀ andmay obtain Ru and Ru⁽¹⁾ at time t₁ after 36.48 ns from time t₀, using asignal received from an i-th antenna. Here, it is assumed that thereception apparatus 102 can predict a channel measurement interval usingR_(u) and R_(u) ⁽¹⁾ before time t₀. Subsequently, the receptionapparatus 102 may obtain R_(v) and R_(v) ⁽¹⁾ at time t₂ after 292 nsfrom time t₀ and may obtain R_(v) and R_(v) ⁽¹⁾ at time t₃ after 292 nsfrom time t₁. The reception apparatus 102 may add R_(u) obtained at timet₀ and R_(v) obtained at time t₂ and may add R_(u) ⁽¹⁾ obtained at timet₀ and R_(v) ⁽¹⁾ obtained at time t₂, thereby estimating channels hi1and hi2. Further, the reception apparatus 102 may add R_(u) obtained attime t₁ and R_(v) obtained at time t₃ and may add R_(u) ⁽¹⁾ obtained attime t₁ and Rv⁽¹⁾ obtained at time t₃, thereby estimating channelsh_(i3) and h_(i4).

FIG. 24 illustrates the operation procedure of a transmission apparatusaccording to an exemplary embodiment of the present disclosure. Here,for convenience of explanation, it is assumed that a 2×2 MIMO system issupported. However, the following operation may be applied to an N×NMIMO system in the same manner. In addition, the order of the operationsdescribed below is provided only for illustration and does not limit thepresent disclosure. For example, the order of operations described belowmay be changed depending on the design.

Referring to FIG. 24, the transmission apparatus 100 may generate afirst Golay sequence and a second Golay sequence in operation 2401. Forexample, the transmission apparatus 100 may generate the first Golaysequence based on a first seed and the second Golay sequence based on asecond seed. More specifically, the transmission apparatus 100 maygenerate the first Golay sequence by applying Dn and Wn represented byEquation 2 to Equation 1 using Dn and Wn as seeds. Further, thetransmission apparatus 100 may generate the second Golay sequence byapplying Dn and Wn represented by Equation 9 to Equation 1. Here, thefirst Golay sequence may include at least one of Ga₁₂₈(k), Gb₁₂₈(k),Gu512(k), and Gv512(k). The second Golay sequence may include at leastone of G⁽¹⁾a₁₂₈(k), G⁽¹⁾b₁₂₈(k), G⁽¹⁾u512, and G⁽¹⁾v512(k). Here, thesecond seed may be determined in consideration of the correlationbetween a Golay sequence to be generated based on the second seed and aGolay sequence to be generated based on the first seed.

The transmission apparatus 100 generates a first reference signalincluding the first Golay sequence and a second reference signalincluding the second Golay sequence in operation 2403. For example, thetransmission apparatus 100 generates a first CEF 800 as illustrated inFIGS. 8A and 8B based on the first Golay sequence obtained based on thefirst seed, and generates a first reference signal including thegenerated first CEF. The first CEF 800 may sequentially include −Ga128,Gu512, Gv512, and −Gb128. Here, Gu512 may sequentially include −Gb128,−Ga128, Gb128, and −Ga128, and Gv512 may sequentially include −Gb128,Ga128, −Gb128, −Ga128. The transmission apparatus 100 also generates asecond CEF 810 as illustrated in FIG. 8A or a second CEF 820 asillustrated in FIG. 8B based on the second Golay sequence obtained basedon the second seed, and generate a second reference signal including thesecond CEF. The second CEF 810 may sequentially include −Ga128,G⁽¹⁾u512, G⁽¹⁾v512, and −G⁽¹⁾b128. Further, the second CEF 820 maysequentially include −G⁽¹⁾a128, G⁽¹⁾u512, G⁽¹⁾v512, and −G⁽¹⁾b128. Here,G⁽¹⁾u512 may sequentially include −G⁽¹⁾b128, −G⁽¹⁾a128, G⁽¹⁾b128, and−G⁽¹⁾a128, and G⁽¹⁾v512 may sequentially include −G⁽¹⁾b128, G⁽¹⁾a128,−G⁽¹⁾b128, and −G⁽¹⁾a128.

The transmission apparatus 100 transmits the first reference signal andthe second reference signal through a first antenna and a secondantenna, respectively, in operation 2405. For example, as illustrated inFIG. 9, the transmission apparatus 100 transmits the first referencesignal including the first CEF 800 using the first antenna and transmitsthe second reference signal including the second CEF 810 using thesecond antenna.

Subsequently, the transmission apparatus 100 terminates the operationprocedure according to the exemplary embodiment of the presentdisclosure.

The exemplary embodiment of the present disclosure shows that differentGolay sequences are generated using different seeds. However, usingdifferent seeds is merely an example and does not limit the presentdisclosure. For example, the transmission apparatus 100 may generatedifferent Golay sequences using different methods. In another example,the transmission apparatus 100 may use different Golay sequences storedin advance in a memory.

FIG. 25 illustrates the operation procedure of a transmission apparatusaccording to another exemplary embodiment of the present disclosure.Here, for convenience of explanation, it is assumed that a 2×2 MIMOsystem is supported. However, the following operation may be applied toan N×N MIMO system in the same manner. In addition, the order of theoperations described below is provided only for illustration and doesnot limit the present disclosure. For example, the order of operationsdescribed below may be changed depending on the design.

Referring to FIG. 25, the transmission apparatus 100 generates a Golaysequence in operation 2501. For example, the transmission apparatus 100may generate the Golay sequence based on one seed. More specifically,the transmission apparatus 100 may generate the first Golay sequence byapplying Dn and W_(n) represented by Equation 2 to Equation 1 usingD_(n) and W_(n) as seeds. Here, the first Golay sequence may include atleast one of Ga₁₂₈(k), Gb₁₂₈(k), Gu512(k), and Gv512(k).

The transmission apparatus 100 generates a first reference signal and asecond reference signal that include the same Golay sequence inoperation 2503. For example, the transmission apparatus 100 generates afirst CEF 1400 and a second CEF 1410 as illustrated in FIG. 14 based onthe first Golay sequence obtained based on the first seed. Here, thefirst CEF 1400 and the second CEF 1410 may sequentially include −Ga128,Gu512, Gv512, and −Gb128. Here, Gu512 may sequentially include −Gb128,−Ga128, Gb128, and −Ga128, and Gv512 may sequentially include −Gb128,Ga128, −Gb128, and −Ga128. The transmission apparatus 100 generates thefirst reference signal including the first CEF 1400 and the secondreference signal including the second CEF 1410.

The transmission apparatus 100 transmits the first reference signalthrough a first antenna in operation 2505. For example, the transmissionapparatus 100 transmits the first reference signal including the firstCEF 1400 illustrated in FIG. 15 to a reception apparatus 102 at a firsttime through the first antenna.

The transmission apparatus 100 transmits the second reference signalthrough a second antenna at a time delayed from the transmission time ofthe first reference signal in operation 2507. For example, thetransmission apparatus 100 transmits the second reference signalincluding the second CEF 1410 illustrated in FIG. 15 to the receptionapparatus 102 at a second time through the second antenna. Here, thesecond time is a time after a predetermined time from the first time.

Subsequently, the transmission apparatus 100 terminates the operationprocedure according to the exemplary embodiment of the presentdisclosure.

FIG. 26 illustrates the operation procedure of a reception apparatusaccording to an exemplary embodiment of the present disclosure. Here,for convenience of explanation, it is assumed that a 2×2 MIMO system issupported. However, the following operation may be applied to an N×NMIMO system in the same manner. In addition, the order of the operationsdescribed below is provided only for illustration and does not limit thepresent disclosure. For example, the order of operations described belowmay be changed depending on the design.

Referring to FIG. 26, the reception apparatus 102 receives a signalthrough a first antenna and a second antenna in operation 2601. Forexample, the reception apparatus 102 may receive a reference signaltransmitted from a first antenna and a second antenna of a transmissionapparatus 100 through the first antenna, and may receive a referencesignal transmitted from the first antenna and the second antenna of thetransmission apparatus 100 through the second antenna.

The reception apparatus 102 correlates the received signal of the firstantenna using a first correlator and a second correlator and correlatesthe received signal of the second antenna using the first correlator andthe second correlator in operation 2603. Here, the first correlator andthe second correlator may be configured based on a Golay sequencegenerated by the transmission apparatus 100. For example, when thetransmission apparatus 100 generates a first reference signal isgenerated based on Gu512 and Gv512 and generates a second referencesignal based on G⁽¹⁾u512 and G⁽¹⁾v512, the first correlator may beconfigured based on Gu512 and Gv512, and the second correlator may beconfigured based on G⁽¹⁾u512 and G⁽¹⁾v512.

In operation 2605, the reception apparatus 102 estimates a channel basedon the result of the correlation in operation 2603. For example, thereception apparatus 102 may add the signals resulting from thecorrelation, thereby estimating the channel based on the characteristicthat interference components become impulse signals.

Subsequently, the reception apparatus 102 terminates the operationprocedure according to the exemplary embodiment of the presentdisclosure.

FIG. 27 illustrates the operation procedure of a reception apparatusaccording to another exemplary embodiment of the present disclosure.Here, for convenience of explanation, it is assumed that a 2×2 MIMOsystem is supported. However, the following operation may be applied toan N×N MIMO system in the same manner. In addition, the order of theoperations described below is provided only for illustration and doesnot limit the present disclosure. For example, the order of operationsdescribed below may be changed depending on the design. FIG. 27 assumesthat each antenna employs a single correlator in the reception apparatus102.

Referring to FIG. 27, the reception apparatus 102 receives a signalthrough a first antenna and a second antenna and delays the receivedsignal in operation 2701. For example, the reception apparatus 102 mayreceive a reference signal transmitted from a first antenna and a secondantenna of a transmission apparatus 100 through the first antenna, andmay receive a reference signal transmitted from the first antenna andthe second antenna of the transmission apparatus 100 through the secondantenna. The reception apparatus 102 may temporarily store or delay thereceived signal of the first antenna and the received signal of thesecond antenna using a buffer or a delayer.

The reception apparatus 102 correlates the received signal of the firstantenna using a first correlator and correlates the received signal ofthe second antenna using a second correlator in operation 2703. Here,the first correlator and the second correlator may be configured basedon a Golay sequence generated by the transmission apparatus 100. Forexample, when the transmission apparatus 100 generates a first referencesignal is generated based on Gu512 and Gv512 and generates a secondreference signal based on G⁽¹⁾u512 and G⁽¹⁾v512, the first correlatormay be configured based on Gu512 and Gv512, and the second correlatormay be configured based on G⁽¹⁾u512 and G⁽¹⁾v512.

In operation 2705, the reception apparatus 102 estimates a first channeland a second channel based on the result of the correlation in operation2703. For example, the reception apparatus 102 may add the results ofthe correlation, thereby estimating the channel based on thecharacteristic that interference components become impulse signals.Specifically, as illustrated in FIG. 13, the reception apparatus 102provides signals received from time t₀ to time t₁ to the first andsecond Golay correlators 103-1 and 130-2, thereby obtaining Ru, Ru⁽¹⁾,Rv, and Rv⁽¹⁾. The reception apparatus 102 may add obtained Ru, Ru⁽¹⁾,Rv, and Rv⁽¹⁾, thereby estimating channels h₁ 1 and h₂ 2.

In operation 2707, the reception apparatus 102 correlates the delayedreceived signal of the first antenna using the second correlator andcorrelates the delayed received signal of the second antenna using thefirst correlator. In operation 1209, the reception apparatus 102estimates a third channel and a fourth channel based on the result ofthe correlation in operation 2707. For example, the reception apparatus102 may add the results of correlating the delayed or buffered signals,thereby estimating the channels based on the characteristic thatinterference components become impulse signals. Specifically, asillustrated in FIG. 13, the reception apparatus 102 provides signalsreceived from time t₂ to time t₃ to the first and second Golaycorrelators 103-1 and 130-2, thereby obtaining R_(u), R_(u) ⁽¹⁾, R_(v),and R_(v) ⁽¹⁾. The reception apparatus 102 may add obtained R_(u), R_(u)⁽¹⁾, R_(v), and R_(v) ⁽¹⁾, thereby estimating channels h₁₂ and h₂₁.

Subsequently, the reception apparatus 102 terminates the operationprocedure according to the exemplary embodiment of the presentdisclosure.

FIG. 28 is a block diagram illustrating the configuration of atransmission apparatus according to an exemplary embodiment of thepresent disclosure.

Referring to FIG. 28, the transmission apparatus 100 may include acontroller 2800, a transceiver 2810, and a storage unit 2820, whereinthe controller 2800 may include a reference signal generation unit 2801.

The controller 2800 may include at least one processor. The controller2800 controls a function for the overall operation of the transmissionapparatus. The controller 2800 includes the reference signal generationunit 2801. The reference signal generation unit 2801 may generate andtransmit a reference signal for minimizing a channel estimation errorbased on a Golay sequence. Although not shown, the reference signalgeneration unit 2801 may include a Golay sequence generator 101 togenerate a Golay sequence based on a recursive procedure represented byEquation 1. The reference signal generation unit 2801 may generate a CEFincluding a Golay sequence and may generate a reference signal includingthe generated CEF. The reference signal may include information forchannel estimation and synchronization for a reception apparatus 102.The reference signal generation unit 2801 may generate the CEF byvarious methods depending on the design method. For example, thereference signal generation unit 2801 may generate a first CEF and asecond CEF based on two different seeds as illustrated in FIGS. 8A and8B. In another example, the reference signal generation unit 2801 maygenerate a first CEF and a second CEF based on a single seed asillustrated in FIG. 14. Here, the reference signal generation unit 2801may control the first CEF and the second CEF to be transmitted atdifferent times. Further, the reference signal generation unit 2801 maygenerate first to fourth CEFs based on two different seeds asillustrated in FIGS. 17A and 17B. Further, the reference signalgeneration unit 2801 may generate first to fourth CEFs based on twodifferent seeds as illustrated in FIGS. 20A and 20B. Here, asillustrated in FIGS. 20A and 20B, the reference signal generation unit2801 may control a transmission time for third and fourth CEFs to bedelayed by a certain time or longer from a transmission time for firstand second CEFs.

The transceiver 2810 includes a plurality of antennas. The plurality ofantennas may be an array antenna. The transceiver 2810 transmits asignal to the reception apparatus 102 using the plurality of antennas.The transceiver 2810 may transmit a plurality of reference signals tothe reception apparatus 102 using the plurality of antennas under thecontrol of the controller 2800.

The storage unit 2820 stores various data and programs necessary for theoperation of the transmission apparatus 100. The storage unit 2820 maystore information on a seed necessary to generate a reference signal.For example, the storage unit 2820 may store D_(n) and W_(n) representedby Equation 2 and may store D_(n) and W_(n) represented by Equation 9.

Although FIG. 28 illustrates that the controller 2800 includes thereference signal generation unit 2801, the reference signal generationunit 2801 may be included in the transceiver 2810 depending on thedesign method.

FIG. 29 is a block diagram illustrating the configuration of a receptionapparatus according to an exemplary embodiment of the presentdisclosure.

Referring to FIG. 29, the reception apparatus 102 may include acontroller 2900 and a transceiver 2910, wherein the transceiver 2910 mayinclude a channel estimation unit 2920.

The controller 2900 may include at least one processor. The controller2900 controls a function for the overall operation of the receptionapparatus. The controller 2900 may control the transceiver 2910 tocontrol an operation for estimating a channel from a reference signal.

The transceiver 2910 may include a plurality of antennas. Here, theplurality of antennas may be an array antenna. The transceiver 2910receives a signal transmitted from a transmission apparatus 100 usingthe plurality of antennas. In particular, the transceiver 2910 mayinclude the channel estimation unit 2920. The channel estimation unit2920 performs an operation for estimating a channel between thetransmission apparatus 100 and the reception apparatus 102 from areference signal received from the plurality of antennas. Specifically,the channel estimation unit 2920 may include a Golay correlator 2921 anda delayer 2922. The channel estimation unit 2920 may include one Golaycorrelator 2921 for each receiving antenna or may include a plurality ofGolay correlators for each receiving antenna. Further, the channelestimation unit 2920 may include one or more delayers 2922 for eachreceiving antenna. Here, the Golay correlator 2921 may be configuredbased on a Golay sequence generation method of the transmissionapparatus 100. Therefore, a method for generating and transmitting areference signal based on a Golay sequence may be preconfigured in eachof the transmission apparatus 100 and the reception apparatus 102 or maybe agreed upon between the transmission apparatus 100 and the receptionapparatus 102 through the exchange of signals therebetween. The channelestimation unit 2920 may correlate the signals received through theplurality of antennas using the Golay correlator 2921 and the delayer2922 by the method illustrated in FIG. 13, FIG. 18, or FIG. 23 and mayestimate a channel based on the correlation result. The channelestimation unit 2920 may add particular correlation results, so thatinterference components become 0 in each channel during a channelmeasurement interval. Accordingly, the channel estimation unit 2920 mayestimate each channel without any error.

According to an exemplary embodiment of the present disclosure, forchannel estimation in an MIMO system, different Golay sequences may betransmitted through separate antennas or the same Golay sequence may betransmitted through each antenna at different times, thereby preventingthe occurrence of a channel estimation error.

Although the present disclosure has been described by the restrictedembodiments and the drawings as described above, the present disclosureis not limited to the aforementioned embodiments and variousmodifications and alterations can be made from the descriptions by thoseskilled in the art to which the present disclosure pertains.

Operations according to an embodiment of the present disclosure may beimplemented by a single controller. In this case, program instructionsfor performing various computer-implemented operations may be stored ina computer-readable medium. The computer readable medium may include aprogram command, a data file, a data structure, and the likeindependently or in combination. The program command may be thingsspecially designed and configured for the present disclosure, or thingsthat are well known to and can be used by those skilled in the relatedart. For example, the computer readable recoding medium includesmagnetic media such as a hard disk, a floppy disk, and a magnetic tape,optical media such as a CD-ROM and a DVD, magneto-optical media such asa floptical disk, and hardware devices such as a ROM, RAM, and a flashmemory, which are specially constructed in such a manner that they canstore and execute a program command. Examples of the program commandinclude a machine language code generated by a compiler and a high-levellanguage code executable by a computer through an interpreter and thelike. When all or some of the base stations or relays as described inthe present disclosure are implemented by a computer program, acomputer-readable recording medium in which the computer program isstored also falls within the scope of the present disclosure. Therefore,the scope of the present disclosure should not be defined as beinglimited to the embodiments, but should be defined by the appended claimsand equivalents thereof.

What is claimed is:
 1. A method performed by a transmission apparatus ina wireless communication system, the method comprising: generating firstgolay sequences based on a first seed and a common seed; generatingsecond golay sequences based on a second seed and the common seed;generating a first channel estimation field (CEF) based on the firstgolay sequences, wherein: the first CEF comprises −Ga128, Gu512, Gv512,and −Gb128, the Gu512 sequentially comprises −Gb128, −Ga128, Gb128, and−Ga128, and the Gv512 sequentially comprises −Gb128, Ga128, −Gb128, and−Ga128; and generating a second CEF based on the second golay sequences,wherein: the second CEF sequentially comprises −Ga⁽¹⁾128, G⁽¹⁾u512,G⁽¹⁾v512, and −G⁽¹⁾b128, the G⁽¹⁾u512 sequentially comprises −Gb⁽¹⁾128,−Ga⁽¹⁾128, Gb⁽¹⁾128, and −Ga⁽¹⁾128, and the G⁽¹⁾v512 sequentiallycomprises −Gb⁽¹⁾128, Ga⁽¹⁾128, −Gb⁽¹⁾128, and −Ga⁽¹⁾128, wherein thefirst golay sequences comprises the Ga128 and the Gb128, wherein thesecond golay sequences comprises the Ga⁽¹⁾128 and the Gb⁽¹⁾128, whereinthe common seed comprises a vector D_(n)=[1 8 2 4 16 32 64], and whereinthe first seed comprises a first vector W_(n)=[−1, −1, −1, −1, +1, −1−1] for a first antenna and the second seed comprises a second vectorW_(n)=[+1, −1, −1, −1, +1, −1 −1] for a second antenna.
 2. The method ofclaim 1, wherein the first CEF is used for a transmission associatedwith the first antenna of the transmission apparatus, and wherein thesecond CEF is used for a transmission associated with the second antennaof the transmission apparatus.
 3. The method of claim 1, wherein thefirst golay sequences comprises Ga128(k)=A₇(128-k) andGb128(k)=B₇(128-k), wherein each of the A₇(128-k) and the B₇(128-k) isdetermined according to the following equations:A ₀(k)=δ(k);B ₀(k)=δ(k);A _(n)(k)=W _(n) A _(n−1)(k)+B _(n−1)(k−D _(n)); andB _(n)(k)=W _(n) A _(n−1)(k)−B _(n−1)(k−D_(n)), and wherein, n=1, . . ., N, represents a number of iterations, and k=0, 1, . . . , 2^(N)−1,A_(n)(k) and B_(n)(k) are 0 where k<0, k≥2n, δ(k) represents a deltafunction, D_(n) represents the common seed, and W_(n) represents thefirst seed.
 4. The method of claim 1, wherein a correlation between asequence obtained from the first golay sequences and a sequence obtainedfrom the second golay sequences is zero.
 5. The method of claim 1,wherein a transmission start time for the second CEF is delayed by apredetermined time from a transmission start time for the first CEF. 6.A method performed by a reception apparatus in a wireless communicationsystem, the method comprising: identifying first golay sequencesgenerated based on a first seed and a common seed; identifying secondgolay sequences generated based on a second seed and the common seed;and obtaining a first channel estimation field (CEF) based on the firstgolay sequences and a second CEF based on the second golay sequences,wherein: the first CEF comprises −Ga128, Gu512, Gv512, and −Gb128, theGu512 sequentially comprises −Gb128, −Ga128, Gb128, and −Ga128, and theGv512 sequentially comprises −Gb128, Ga128, −Gb128, and −Ga128, wherein:the second CEF sequentially comprises −Ga⁽¹⁾128, G⁽¹⁾u512, G⁽¹⁾v512, and−G⁽¹⁾b128, the G⁽¹⁾u512 sequentially comprises −Gb⁽¹⁾128, −Ga⁽¹⁾128,Gb⁽¹⁾128, and −Ga⁽¹⁾128, and the G⁽¹⁾v512 sequentially comprises−Gb⁽¹⁾128, Ga⁽¹⁾128, −Gb⁽¹⁾128, and −Ga⁽¹⁾128, wherein the first golaysequences comprises the Ga128 and the Gb128, wherein the second golaysequences comprises the Ga⁽¹⁾128 and the Gb⁽¹⁾128, wherein the commonseed comprises a vector D_(n)=[1 8 2 4 16 32 64], and wherein the firstseed comprises a first vector W_(n)=[−1, −1, −1, −1, +1, −1 −1] for afirst antenna of a transmission apparatus and the second seed comprisesa second vector W_(n)=[+1, −1, −1, −1, +1, −1 −1] for a second antennaof the transmission apparatus.
 7. The method of claim 6, wherein thefirst CEF is used for a transmission associated with the first antennaof the transmission apparatus, and wherein the second CEF is used for atransmission associated with the second antenna of the transmissionapparatus.
 8. The method of claim 6, wherein the first golay sequencescomprises Ga128(k)=A₇(128-k) and Gb128(k)=B₇(128-k), wherein each of theA₇(128-k) and the B7(128-k) is determined following equations:A ₀(k)=δ(k);B ₀(k)=δ(k);A _(n)(k)=W_(n) A _(n−1)(k)+B _(n−1)(k−D _(n)); andB _(n)(k)=W _(n) A _(n−1)(k)−B _(n−1)(k−D _(n)), and wherein, n=1, 2, .. . , N, represents a number of iterations, and k=0, 1, . . . , 2^(N)−1,A_(n)(k) and B_(n)(k) are 0 where k<0, k≥2n, δ(k) represents a deltafunction, D_(n) represents the common seed, and W_(n) represents thefirst seed.
 9. The method of claim 6, wherein a correlation between asequence obtained from the first golay sequences and a sequence obtainedfrom the second golay sequences is zero.
 10. The method of claim 6,wherein the obtaining the first CEF and the second CEF comprises:performing first correlation of a received signal of the first antennaby using a first correlator, and performing second correlation of thereceived signal of the second antenna by using a second correlator, andwherein the first correlator is configured based on the first golaysequences, and the second correlator is configured based on the secondgolay sequences.
 11. A transmission apparatus in a wirelesscommunication system, the transmission apparatus comprising: at leastone transceiver; and at least one processor coupled to the at least onetransceiver, configured to: generate first golay sequences based on afirst seed and a common seed; generate second golay sequences based on asecond seed and the common seed; generate a first channel estimationfield (CEF) based on the first golay sequences, wherein: the first CEFcomprises −Ga128, Gu512, Gv512, and −Gb128, the Gu512 sequentiallycomprises −Gb128, −Ga128, Gb128, and −Ga128, and the Gv512 sequentiallycomprises −Gb128, Ga128, −Gb128, and −Ga128; and generate a second CEFbased on the second golay sequences, wherein: the second CEFsequentially comprises −Ga⁽¹⁾128, G⁽¹⁾u512, G⁽¹⁾v512, and −G⁽¹⁾b128, theG⁽¹⁾u512 sequentially comprises −Gb⁽¹⁾128, −Ga⁽¹⁾128, Gb⁽¹⁾128, and−Ga⁽¹⁾128, and the G⁽¹⁾v512 sequentially comprises −Gb⁽¹⁾128, Ga⁽¹⁾128,−Gb⁽¹⁾128, and −Ga⁽¹⁾128, wherein the first golay sequences comprisesthe Ga128 and the Gb128, wherein the second golay sequences comprisesthe Ga⁽¹⁾128 and the Gb⁽¹⁾128, wherein the common seed comprises avector D_(n)=[1 8 2 4 16 32 64], and wherein the first seed comprises afirst vector W_(n)=[−1, −1, −1, −1, +1, −1 −1] for a first antenna andthe second seed comprises a second vector W_(n)=[+1, −1, −1, −1, +1, −1−1] for a second antenna.
 12. The transmission apparatus of claim 11,wherein the first CEF is used for a transmission associated with thefirst antenna of the transmission apparatus, and wherein the second CEFis used for a transmission associated with the second antenna of thetransmission apparatus.
 13. The transmission apparatus of claim 11,wherein the first golay sequences comprises Ga128(k)=A₇(128-k) andGb128(k)=B₇(128-k), wherein each of the A₇(128-k) and the B₇(128-k) isdetermined following equations:A ₀(k)=δ(k);B ₀(k)=δ(k);A _(n)(k)=W _(d) A _(n−1)(k)+B _(n−1)(k−D _(n)); andB _(n)(k)=W _(n) A _(n−1)(k)−B _(n−1)(k−D _(n)), and wherein, n=1, 2, .. . , N, represents a number of iterations, and k=0, 1, . . . , 2^(N)−1,A_(n)(k) and B_(n)(k) are 0 where k<0, k≥2n, δ(k) represents a deltafunction, D_(n) represents the common seed, and W_(n) represents thefirst seed.
 14. The transmission apparatus of claim 11, wherein acorrelation between a sequence obtained from the first golay sequencesand a sequence obtained from the second golay sequences is zero.
 15. Thetransmission apparatus of claim 11, wherein a transmission start timefor the second CEF is delayed by a predetermined time from atransmission start time for the first CEF.
 16. A reception apparatus ina wireless communication system, the reception apparatus comprising: atleast one transceiver; and at least one processor coupled to the atleast one transceiver, configured to: identify first golay sequencesgenerated based on a first seed and a common seed; identify second golaysequences generated based on a second seed and the common seed; andobtain a first channel estimation field (CEF) based on the first golaysequences and a second CEF based on the second golay sequences, wherein:the first CEF comprises −Ga128, Gu512, Gv512, and −Gb128, the Gu512sequentially comprises −Gb128, −Ga128, Gb128, and −Ga128, and the Gv512sequentially comprises −Gb128, Ga128, −Gb128, and −Ga128, wherein: thesecond CEF sequentially comprises −Ga⁽¹⁾128, G⁽¹⁾u512, G⁽¹⁾v512, and−G⁽¹⁾b128, the G⁽¹⁾u512 sequentially comprises −Gb⁽¹⁾128, −Ga⁽¹⁾128,Gb⁽¹⁾128, and −Ga⁽¹⁾128, and the G⁽¹⁾v512 sequentially comprises−Gb⁽¹⁾128, Ga⁽¹⁾128, −Gb⁽¹⁾128, and −Ga⁽¹⁾128, wherein the first golaysequences comprises the Ga128 and the Gb128, wherein the second golaysequences comprises the Ga⁽¹⁾128 and the Gb⁽¹⁾128, wherein the commonseed comprises a vector D_(n)=[1 8 2 4 16 32 64], and wherein the firstseed comprises a first vector W_(n)=[−1, −1, −1, −1, +1, −1 −1] for afirst antenna of a transmission apparatus and the second seed comprisesa second vector W_(n)=[+1, −1, −1, −1, +1, −1 −1] for a second antennaof the transmission apparatus.
 17. The reception apparatus of claim 16,wherein the first CEF is used for a transmission associated with thefirst antenna of the transmission apparatus, and wherein the second CEFis used for a transmission associated with the second antenna of thetransmission apparatus.
 18. The reception apparatus of claim 16, whereinthe first golay sequences comprises Ga128(k)=A₇(128-k) andGb128(k)=B₇(128-k), wherein each of the A₇(128-k) and the B₇(128-k) isdetermined according to the following equations:A ₀(k)=δ(k);B ₀(k)=δ(k);A ₁(k)=W _(n) A _(n−1)(k)+B _(n−1)(k−D _(n)); andB _(n)(k)=W _(n) A _(n−1)(k)−B _(n−1)(k−D _(n)), and wherein, n=1, 2, .. . , N, represents a number of iterations, and k=0, 1, . . . , 2^(N)−1,A_(n)(k) and B_(n)(k) are 0 where k<0, k≥2n, δ(k) represents a deltafunction, D_(n) represents the common seed, and W_(n) represents thefirst seed.
 19. The reception apparatus of claim 16, wherein acorrelation between a sequence obtained from the first golay sequencesand a sequence obtained from the second golay sequences is zero.
 20. Thereception apparatus of claim 16, wherein, to obtain the first CEF andthe second CEF, the at least one processor is configured to: performfirst correlation of a received signal of the first antenna by using afirst correlator, and perform second correlation of the received signalof the second antenna by using a second correlator, and wherein thefirst correlator is configured based on the first golay sequences, andthe second correlator is configured based on the second golay sequences.